gtk_toggle_button_set_mode ()

Sets whether the button is displayed as a separate indicator and label.
You can call this function on a checkbutton or a radiobutton with
draw_indicator = FALSE to make the button look like a normal button

gtk_toggle_button_set_inconsistent ()

If the user has selected a range of elements (such as some text or
spreadsheet cells) that are affected by a toggle button, and the
current values in that range are inconsistent, you may want to
display the toggle in an "in between" state. This function turns on
"in between" display. Normally you would turn off the inconsistent
state again if the user toggles the toggle button. This has to be
done manually, gtk_toggle_button_set_inconsistent() only affects
visual appearance, it doesn't affect the semantics of the button.